Thanks for that. I have tried isolating the pipes with new rubber washer, no change.
I have the same rear plug carbon issue as you. The vibration on mine happened gradually over about 1000km's. Sometimes it's worse and at certain revs (cruising) on a good day I cant feel it until I throttle on.
I dont want to do what you did and pull the engine for nothing. The bike runs well, has a flat spot as I throttle from idle and sometimes backfires(more of a gasp). My concern is that under load, say 100kmph and throttling on, the whole bike vibes badly and there's a loss of power. Particularly noticeable in head winds. I've checked everything you have as well. Frustrating coz it ruins my rides.
1998 Custom Classic.